Thermostatic switch



June 20, 1933. R w. MCBRIEN ET AL 1,914,725

THERMOSIATIC SWITCH Filed June 18,- 1930 VENTDES Patented June 20, 1933 UNITED STATES PATENT OFFICE ROGER W. MCBRIEN, OF ALTON, AND NORVAL F. WILSON, OF EAST ALTON, ILLINOIS THERMOSTATIG SWITCH Application filed June 18,

Our invention has relation to improvements in thermostatically operated switches adapted for use in alarm circuits, and it consists in the novel features of construction 4 more fully set forth in the specification and pointed out in the claims. The present invention is an improvement over that shown in our pending application Ser. No. 421,387 filed January 17, 1930 and has for its object the provision of a thermostatic switch wherein liquids such as mercury, used in the application mentioned, may be dispensed with. A further object of the invention is to provide a switch that may easily and quickly be reset after having been put into operation by heat caused by an overload or short in the circuit protected by the switch. It is also an object of the present invention to provide a switch of this type that is simple and capable of being manufactured at low cost, and one that may be operated repeatedly without its efliciency being impaired. The manner of accomplishing the above objects together with other advantages will be better apparent from a detailed description thereof in connection with the accompanying drawing, in which Fig. 1 shows an electric circuit diagrammatically, with our improved switch connected therein in a manner to perform the function for which it is designed; Figs. 2 to inclusive, show modifications of the switch construction, the circuit arrangement being the same in each instance.

Referring to the drawing 1, 1 indicate the wires of an electric circuit for furnishing power to any electrically operated apparatus which may be connected to the outlets for the lamps 2, 2, such lamps merely indicating a load on the circuit, which obviously may be of any extent. Our improved thermostatically operated switch S which is adapted to protect the circuit comprised in the wires 1, 1 includes an insulating panel 3 from which is suspended by means of a flexible arm, or spring, 4 a contact plate 5. The arm 4 is, of course, a conductor and is secured to the panel by means of a screw 6 which also serves as a binding screw for one end of the con 1930. Serial No. 461,958.

8, consisting preferably of fuse wire, said conductor 8 sliding freely through the thimble and being gripped by a pair of spring fingers 9, 9 disposed between the panel and contact plate 5. The fingers 9, 9 are secured to the panel by means of screws 10, 10, the

former serving as a binding post for line wire 1. As shown in Fig. 1, the fuse wire 8, if pushed far enough through the fingers 9, 9 will serve as an abutment for the contact plate 5 and hold said plate away from the series of contacts 11, 12, and 13 projecting from the panel 3 and secured thereto by screws 14, 15, and 16. Each of the screws 14, 15, and 16 serves as a binding post for conductors of the circuit, of which conductor 17 leads from screw 16 to line wire 1, and has connected in series with it a resistance 18; conductor 19 leads from screw 15 to line wire 1", and conductor 20 leads from screw 14 to one side of the coil 21 of a relay 22, the other side of said relay coil being connected to conductor 19 by a conductor 23. There is also an indicator lamp 24 connected in series with conductor 19. When the switch S is in its operative position, the contact plate 5 is propped by the fuse wire 8 so that it is not in contact with the three contacts 11, 12, and 13. The flow of the current to the lamps 2 is from the line wire 1 through the lamps to conductor 1 thence through the spring arm 4 and plate 5 to fuse wire 8, finger 9, and line wire 1". Should there be a momentary short circuit between line wire 1 and conductor 1 the high current flow will destroy that part of the fuse between fingers 9, 9 and plate 5 causing said plate to snap down onto the contacts 11, 12, and 13. The flow of current through the lamps 2 will then be from line wire 1 through conductor 17 and resistance 18, binding post 16, contact 13, plate 5, contact 12, conductor 19 and lamp 24 thence to line wire 1. The resistance 18 of course, consumes considerable of the current flowing through the circuit and since the circuit is not out of commission (a short having been assumed to be temporary) the lamp 24 will glow dimly and indicate the nature of the trouble.

At the same time the relay 22 has been actuated by the current from line wire 1, conduct-or 17, contact 13, plate 5, contact 11, conductor 20, relay coil 21, conductor 23, and back to line wire 1". This relay may be connected to a tire or police alarm or any other kind of alarm desired.

If the short circuit between line wire 1 and line wire 1 is of a permanent nature the heavy current flow from line wire 1 to conductor 1 through arm at, plate 5, contact conductor 19. and lamp 2st will cause said indicator lamp to burn brightly indicating to an observer that the switch was actuated by a short circuit which is still in effect, or permanent in its nature.

Having remedied the trouble the operator may restore the circuit to its operative condition by merely pushing the fuse wire forward through the lingers 9, 9 so that it again moves the plate 5 away from contacts 11, 12, and 13.

In the modification shown in Fig. 2, the contact plate 5' makes contact only with the fuse wire prop 8. Instead of said plate being supported by a spring arm it forms one end of lever 25 pivoted at -26, the opposite end of said lever supporting weight 27 over an insulated receptacle 28 in which a body of mercury 29. A series of conductors 30. 31. 32, and 33 which form a. part of the circuit across the receptacle 28 so that the mercury 29 will make contact with them when it is displaced by the weight 2. upon the destruction of the fuse prop 8 in the event of a short circuit.

In Fig. 3 we show a modifi "ation wherein the contact plate 5 is pivotally supported at 26 and carries on the short lever arm 3-1 a closed tube 35 of insulating material in which is a body of mercury 36 adapted to flow to the opposite end of the tube when the fuse prop 8 is destroyed and make contact between conductors 37, 3S, and 39 which traverse said tube.

In Figs. 4 and 5 we show a modification wherein, what might be termed, a fuse strip -10 is used to operate a hinged contact plate 11. This strip 40 is traversed by a series of fuse wires 42, 12 each of which has a fuhninating cap 43 associated with it and disposed within a recess M in the body of the strip 40 which is of insulating material. Oppositely disposed pairs of gripping fingers 15 are provided to recei 'e the extremities of the fuse wires 42. Suitable conductors -16. 4-7 are connected to the fingers 45, and into the circuit that is protected by our fuse assembly. Should an excessive current flow through this circuit the fuse wire 42 is destroyed in the usual manner and the cap 43 exploded. The effect of the explosion is effective on the plate 41 through the open bottom of recess 44 and forces said plate past the spring detent 46' causing it to engage the contacts 48, 49 which closes the alarm circuit (not shown).

Having described our invention, we claim:

1. A thermostatically operated switch comprising an insulating panel, a contact element hingedly supported thereby, a plurality of electric contact-s adapted to be engaged by said contact element, a fuse metal conductor disposed substantially perpendicular to said element, gripping elements for holding the fuse metal conductor in a manner to permit sliding said conductor toward the contact element to move same away from the electric contacts.

2. A thermostatically operated switch comprising a suitable support, a contact element hingedly supported thereby, an electric contact arranged to be engaged by said contact element, means for normally holding said element in spaced relation with the electric contact, said means comprising a conductor adapted to be partially destroyed by the heat of an excessive current to release said ele ment, the remainder of the conductor being movable to again effect a spacing of the element and contact.

A thermostatically operated switch comprising a suitable support, a contact element hingedly supported thereby, an electric contact arranged to be engaged by said element, means for normally holding said element in spaced relation with the electric contact, gripping elements for said holding means adapted to permit adjustmentof said means to hold said means where desired, a part of said holding means being destructible by the heat of an excessive current flow to release said element, the remainder of the holding means being movable in the gripping elements to restore the spaced relation between element and contact.

t. A thermostatically operated switch comprising a suitable support, a contact element hingedly supported thereby, a. switch contact in juxtaposition to the contact element, a fuse holder, and a fuse element adapted to traverse said holder to engage the contact element and hold said element in spaced relation with the switch contact, said contact element being arranged to impinge on the switch contact with the removal of the fuse element.

In testimony whereof we hereunto afiix our signatures.

ROGER IV. MCBRIEN. NORVAL F. VILSON. 

